Proper inflation of automotive or other tires currently relies on near perfect sealing of tires to tire rims and excellent performance of tire valves, together with periodic monitoring of tire pressure and re-fill as necessary. Improper tire inflation causes reduced gasoline mileage, abnormal wear patterns, dramatically reduced tire life, and poor safety performance. However, most users persistently demonstrate an unwillingness to monitor and maintain proper tire inflation, typically with the assistance with a filling station pressurized air supply or pump.
Alternative techniques to the filling station air pump for monitoring and adjusting tire pressure are known. For example, U.S. Pat. No. 4,924,926 to Schultz et al. discloses a central tire inflation system having a central pressure distribution and monitoring system which allows tire pressure to be monitored and changed using dashboard controls. Inadequacies of this system include difficulty in sealing joints between the central pressure distribution and the rotating tire rim and tire. Additionally, the Schultz system requires significant investment in vehicle mounted equipment, and it is not easily used with conventional tire mountings or rims.
Another inflation system is disclosed by U.S. Pat. No. 5,119,856 to Zarotti, wherein tire pressure is adjusted with an inflatable bladder internal to the tire, the bladder containing a two-phase material responsive to a thermoelectric heater/cooler. A pressure sensor monitors tire inflation pressure while power is delivered to the tire through an electromagnetic coupling mounted partially on the stationary portion of a car and partially on each tire. Control information is delivered through a modulated carrier transmitted through the electromagnetic coupling, and is locally compared to the monitored tire pressure. Problems with the Zarotti device include the requirement to maintain tire inflation at an adequate level prior to the servo startup, relatively slow adjustment to operating pressure level following startup, and the requirement for vehicle modification to accommodate the system.
U.S. Pat. No. 4,922,984 to Dosjoub et al., discloses entirely mechanical means for automatically maintaining proper tire inflation. However, the reliance on mechanical techniques yields high cost and low reliability.
U.S. Pat. No. 4,349,064 to Booth discloses means for pumping air into a tire by using changes in centrifugal force pursuant to changes in vehicle speed. As the centrifugal force increases, a weight compresses a spring, and this motion is converted into pumping action. Again, the reliance on mechanical techniques yields high cost and low reliability.
U.S. Pat. No. 4,651,792 to Taylor pumps air by using changes in the centrifugal force as seen by a tread-mounted device during each rotation of the tire. As the portion of the tire with the tread-mounted device comes in contact with the ground, that portion undergoes deformation which changes the effective radius of the tire, thus changing the centrifugal force. As the centrifugal force increases, a weight compresses a spring, and this motion is converted into pumping action. Again, the reliance on mechanical techniques yields high cost and low reliability.
It would therefore be desirable to pump a gas between a plenum, such as a tire, and a point exterior to the plenum, without the power, size, weight, and cost of pump assemblies presently available.